By Alexa Staley Contributors S Dwyer D Sigg J Kissel C Wipf Outline of Talk What is ALS The Simulink model What does it consist of Validating the model Noise budget using the model ID: 789235
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Slide1
ALS HIFO-X Noise Budget and Model Status Report
By Alexa Staley
Contributors: S. Dwyer, D.
Sigg
, J.
Kissel
, C.
Wipf
Slide2Outline of Talk
What is ALS?
The
Simulink
model
What does it consist of?
Validating the model.
Noise budget using the model
Comparison to HIFO-Y
Future Plans
Slide3Outline of Talk
What is ALS?
The
Simulink
model
What does it consist of?
Validating the model.
Noise budget using the model
Comparison to HIFO-Y
Future Plans
Slide4Arm Length Stabilization
ALS is an independent locking scheme; allows us to decouple the arm cavities from the interferometer.
The ALS holds the arm cavities off resonance from the PSL beam for easy locking of the recycling cavities.
Once the recycling cavities are locked, ALS brings the arm cavity into resonance with the PSL beam.
Slide5How do we do this?
Using an auxiliary laser at the end station that has both IR and green light, we …
Lock the IR auxiliary beam to the PSL frequency.
Lock the green auxiliary beam to the arm cavity.
Compare the green frequency to the PSL doubled frequency; and eventually bring the PSL light resonant in arm.
Slide6ALS Schematic
1.
2.
3.
Slide7Outline of Talk
What is ALS?
The
Simulink
model
What does it consist of?
Validating the model.
Noise budget using the model
Comparison to HIFO-Y
Future Plans
Slide8Simulink Model
Slide9Simulink Model
Consists of function blocks that are defined in a control script. The control scripts defines the properties (
zpk’s
) of all the servo parts in the ALS.
Uses
LiveParts
for the filters.
Besides the control script, there is a second script in place to validate the model.
A third script to produce the noise budget.
Slide10Servo Loops in Model
End-X Phase locking loop (PLL)
End-X Pound-
Drever
-Hall Loop (PDH)
Corner Station COMM PLL
beatnote
Corner Station Input Mode Cleaner Loop (IMC)
MC2 Suspension stage
COMM handoff path for CARM feedback
Slide11End-X PLL Loop
Uses a phase locked loop to lock the IR auxiliary laser to the frequency transmitted fiber light of the PSL.
Consists of
PLL Common Mode Board Servo
Phase Frequency Discriminator (PFD)
PZT response
Tuned VCO and PFD used for error signal
Slide12ALS Schematic
Slide13End-X PLL Loop Validation
Slide14End-X PDH Loop
With the EX PLL locked, we employ a PDH locking scheme to lock the green auxiliary laser from the end station to the arm cavity.
Consists of:
PDH Common Mode Servo Board
Voltage Controlled Oscillator (VCO)
Cavity pole (1.46kHz * different from HIFOY).
Optical gain of cavity ~1kHz/V
Slide15ALS Schematic
Slide16Validating End-X PDH Loop
Slide17IMC Loop
This loop consists of the mode cleaner lock with a feedback to the MC2 suspension.
Consists of:
IMC cavity pole: ~8kHz
VCO
MC Common Mode Board
Optical gain: 3kHz/V
Slide18ALS Schematic
Slide19IMC Loop Validation
Slide20MC2 Loop
The test mass hangs from a triple suspension; we can actuate on any of three.
Model a simplified version of the loop
Use un-damped HSTS model
Assumes coil driver and coil output exactly cancels
Mystery gain of 1/4
Slide21MC2 Loop Validation
Slide22COMM PLL Beatnote
PLL lock of the green transmitted light through the arm with a frequency doubled light from the PSL.
Locks the green
beatnote
controlling the common mode to the corner
VCOs
Consists of:
PFD
VCO
PLL Board
Slide23ALS Schematic
Slide24COMM PLL Loop Validation
Slide25COMM Handoff
In preparation for locking the IR to the arm (i.e. handing-off from green to IR), we run the COMM handoff.
This feedbacks the COMM
beatnote
frequency to the IMC and the MC2 suspension.
The slow path is feedback to the MC2 suspensions, while the fast path is feedback to the IMC
Crossover between fast and slow: 13Hz
Slide26COMM Handoff Validation
Slide27Outline of Talk
What is ALS?
The
Simulink
model
What does it consist of?
Validating the model.
Noise budget using the model
Comparison to HIFO-Y
Future Plans
Slide28End X PLL Noise Budget in Loop
Slide29End X PLL Noise Budget Out of Loop
Slide30End X PDH Noise Budget
Slide31COMM PLL Noise Budget
Slide32IR Noise Budget
Slide33Outline of Talk
What is ALS?
The
Simulink
model
What does it consist of?
Validating the model.
Noise budget using the model
Comparison to HIFO-Y
Future Plans
Slide34In Comparison to HIFOY
Slide35In Comparison to HIFOY
Slide36Outline of Talk
What is ALS?
The
Simulink
model
What does it consist of?
Validating the model.
Noise budget using the model
Comparison to HIFO-Y
Future Plans
Slide37Future Plans
Continue to search for the 1/f noise in HIFOX (and reduce RMS)
Repeat HIFOY with new configuration
Develop a version of the model to be used in Chris’s full IFO noise budget.
Slide38THE END
Slide39Slide40COMM Handoff Basic Block Diagram
COMM PLL
COMMON PATH
FAST PATH
SLOW PATH
IMC LOOP
MC2 LOOP